An opinion poll uses random digit dialing equipment to dial 2000 randomly chosen residential telephone numbers. Of these, 621 are unlisted numbers. This isn’t surprising, because 35% of all residential numbers are unlisted. Is each of the boldface numbers a parameter or a statistic?
(621 and 35% are the boldfaced numbers)
A ‘Parameter’ is a value that describes a ‘population’.
A ‘Statistic’ is a value that describes a ‘sample’.
Furthermore, a ‘population’ is all of the individuals of interest in a particular study (eg. ALL residential phone numbers). A ‘sample’ is a group of individuals who are selected from a population in order to be studied (eg. the 2000 people randomly called; they are randomly selected from the entire population of residential phone numbers).
So, to answer your question:
621 is a statistic (it refers to the number of unlisted numbers in the study; in the SAMPLE of residential phone numbers)
35% is a parameter (it refers to the number of unlisted numbers in the entire POPULATION of residential phone numbers)
I hope this helps!